This invention relates to heat-resistant lubricant compositions for processing synthetic fibers.
In general, a lubricant is attached to thermoplastic synthetic fibers such as polyester, polyamide and polypropylene immediately after they are melted and spun. After they are made into drawn yarns with different forms and characteristics, they are further subjected to higher-order processes to obtain final products. Recently, the trend has been to speed up these production and processing steps and, in order to improve productivity by using energy-saving means in the production and processing steps of thermoplastic synthetic fibers or by making such steps shorter, attempts are being made to produce partially oriented yarns (POY) and to carry out drawing and false twisting successively or simultaneously by using the POY to thereby produce textured yarns. Currently, there are increasing attempts to speed up these processes but, as the speed of these processes increases, there arise at the same time the needs for a new kind of lubricant which satisfy the following two conditions. One of these conditions to be satisfied is that the lubricant must be able to provide high degrees of lubricity, cohesiveness and antistatic characteristics to feed yarns for false twisting and, in particular, to feed yarns for drawing and false twisting because there is an increase not only in the speed of yarns running in contact with rollers, guides, heaters for heat treatments, disks and the like (hereinafter simply referred to as contact members) but also their contact pressure against them. The other condition to be satisfied relates to the increased amount of substances of all kinds which fall onto the heater because more yarns pass through the heater per unit time and the centrifugal force associated with the twisting of the yarns is also increased. Since both the length of the heater and its surface temperature are increased in order to supply sufficient heat to filaments for winding and securing, furthermore, these substances are degraded more easily. Such thermally degraded substances (such as tar) cause fluffs, yarn breakage, and other ill-effects if they pile up on the heater surface. In view of the above, the lubricant must be able to reduce the amount of substances falling onto the heater.
In the past, many kinds of lubricant compositions containing an ionic or nonionic surfactant as antistatic agent have been used for the processing of synthetic fibers. With conventional lubricant compositions for synthetic fibers, however, the mixing ratio of the antistatic agent must be increased if a high antistatic characteristic is desired. In this case, if the ionic surfactant is sodium alkane sulfonate, potassium alkyl phosphate or the like having metallic ions as counter ions, for example, it lacks in compatibility with the lubricant composition and tends to be rejected from the lubricant system. As a result, it is easily dropped during processing and piled up, thereby increasing the contact friction between fibers and the contact members, causing an increase in the tension, damage to the fibers, fluffs and yarn breakage, and significantly affecting work efficiency and the yarn quality adversely. If the substances which fall off are piled up on the heater for heat treatment and become thermally degraded (such as when tar is generated), the situation is even worse. If the mixing ratio of ionic surfactant is reduced in order to reduce the amount of substances which fall off and become degraded, or if use is made of a nonionic surfactant which is relatively compatible with lubricant compositions, on the other hand, antistatic characteristics cannot be attained as desired and there arise problems due to generated static electricity such as disheveling of filaments, swinging motion of yarns and their wrapping around the rollers. Thus, processability and yarn quality are also adversely affected.
Use of ionic surfactants not having metallic ions as counter ions has been disclosed, for example, in U.S. Pat. Nos. 4,038,258 and 4,506,070 (use of various phosphonium salts) and U.S. Pat. No. 2,837,446 (use of N substituted phosphonium salts). Japanese Patent Publication Tokkai 56-31077 has disclosed the use of polyether compounds for the specific purpose of improving heat resistance. U.S. Pat. Nos. 4,552,671 and 4,561,987 have disclosed the mixing of a polyether compound with polyoxyalkylene modified polysiloxane and an anionic surfactant such as sulfonates, sulfates, phosphates and carboxylates having an alkali metal salt or organic amine salt as counter ions. None of these prior art examples, however, can be a solution to the aforementioned problems as a whole although there are differences in degree among them.